1. Field of the Invention
The present invention relates to a method for treating a substrate, and more particularly to a method for reduced damage removal of residue on a substrate following an etching process.
2. Description of Related Art
During semiconductor processing, a (dry) plasma etch process can be utilized to remove or etch material along fine lines or within vias or contacts patterned on a silicon substrate. The plasma etch process generally involves positioning a semiconductor substrate with an overlying patterned, protective mask layer, for example a photoresist layer, in a processing chamber. Once the substrate is positioned within the chamber, an ionizable, dissociative gas mixture is introduced within the chamber at a pre-specified flow rate, while a vacuum pump is throttled to achieve an ambient process pressure. Thereafter, a plasma is formed when a fraction of the gas species present are ionized by electrons heated via the transfer of radio frequency (RF) power either inductively or capacitively, or via microwave power using, for example, electron cyclotron resonance (ECR). Moreover, the heated electrons serve to dissociate some species of the ambient gas species and create reactant specie(s) suitable for the exposed surface etch chemistry. Once the plasma is formed, selected surfaces of the substrate are etched by the plasma. The process is adjusted to achieve appropriate conditions, including an appropriate concentration of desirable reactant and ion populations to etch various features (e.g., trenches, vias, contacts, etc.) in the selected regions of the substrate. Such substrate materials where etching is required include silicon dioxide (SiO2), low dielectric constant (i.e., low-k) dielectric materials, poly-silicon, and silicon nitride. Once the pattern is transferred from the patterned mask layer to the underlying layer, using, for example, dry plasma etching, the remaining layer of photoresist, and post-etch residues, are removed via an ashing (or stripping) process. For instance, in conventional ashing processes, the substrate having the remaining photoresist layer is exposed to an oxygen plasma formed from the introduction of diatomic oxygen (O2) and ionization/dissociation thereof. However, formation of plasma in close proximity with the substrate can lead to uncontrolled exposure to high energy charged particles (e.g., energetic electrons, etc.) and electro-magnetic (EM) radiation (e.g., ultraviolet (UV) radiation), which may cause damage to underlying layers and/or structures that is unacceptable to the device manufacturers.